Master's Theses

Date of Award

2016

Document Type

Thesis

First Advisor

Shubha Govind

Second Advisor

Jonathan Levitt

Keywords

host prasite, immune supresion, virus-like particles

Abstract

Endoparasitioid wasps of Drosophila spp. frequently avoid or overcome the immune defense mechanisms of their fly hosts. Leptopilina heterotoma (Lh) is a generalist wasp species, successful on many Drosophila spp. world-wide. During oviposition, the female wasp introduces venom proteins and virus-like particles (VLPs) into developing fly larvae. VLPs are endocytosed by plasmatocytes, a macrophage-like blood cell that is the most abundant hemocyte present in the circulating hemolymph. Once internalized, VLPs destroy plasmatocytes by programmed cell death. To understand the contributions of VLP proteins in VLP trafficking within host cells, we took advantage of proteomic data from purified Lh VLPs. Two novel enzymes encoded by venom gland cDNA clones 9A08 and 2E04 were identified. To understand how 9A08 exerts virulence, an unbiased and comprehensive Synthetic Genetic Array (SGA) screen covering all yeast genes was done to identify the cellular pathways or genetic networks most affected by 9A08 overexpression. While several potential categories of functionality were discovered, the most relevant interactions pointed to 9A08 functioning in retrograde transport and vacuolar protein sorting, leading us to hypothesize that 9A08 helps mediate endocytosis of VLPs in fly plasmatocytes. We will also discuss the precise endocytic retrograde trafficking routes that VLPs take before they are disposed or kill plasmatocytes. The most prominent co-localization of p40 occurred with compartmental marker signals of the late endosomes, marked by Rab7-GFP; higher VLP signals correlated with late endosomes in plasmatocytes for animals that underwent a longer post-infection recovery time. Some colocalization of VLP was also observed with the Rab5-GFP as well.

Available for download on Thursday, August 23, 2018

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Biology Commons

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